Vaccines have helped the U.S. and the world mostly return to normal after the COVID-19 pandemic. Researchers say vaccines may not provide the same levels of protection for everyone.

A study from the Cleveland Clinic shows just how big that difference can be. The researchers found vaccinated patients with cancer had a 24 percent higher risk of breakthrough infections than those without cancer. Hospitalization and death rates were between 7 and 14 times higher.

The findings highlight the increased risks people with compromised immune systems face even after vaccination.

But doctors say boosters make a big difference. The researchers stress the importance of the CDC’s recommendation that vulnerable people receive an additional booster vaccine 4 months after their prior dose.